1. Technical Field
Example embodiments relate to a stacked structure of semiconductor devices, a semiconductor device package, and methods of fabricating the same.
2. Description of Related Art
Packaging technologies for integrated circuits (ICs) have been steadily improving to keep up with demands for miniaturization and/or mounting reliability. The demand for miniaturization has accelerated technical developments in the semiconductor chip packaging area, achieving a degree of miniaturization even as small as the actual size of a typical semiconductor chip. Mounting reliability may also be important to packaging, providing mounting efficiency and mechanical/electrical reliability after mounting the semiconductor chips.
Driven by continuing demands for increased performance along with miniaturization of electronics, there have been a variety of efforts to provide higher-capacity semiconductor products. The conventional method of making higher-capacity (enlarged storage capacity) semiconductor products may involve higher-density integration of the semiconductor memory chips. Higher-density integration of memory chips may be accomplished by placing as many memory cells as possible into a given area. However, such two-dimensional integration of the memory cells may require the use of more advanced technology, including microscopic line widths, and/or longer development terms. Accordingly, stacking has been proposed as a solution for fabricating improved higher-capacity semiconductor products.
The term “stacking” is understood in the semiconductor industry to mean a method of vertically stacking two or more semiconductor chips on top of one another. For example, two 64-Mb flash memory chips may be stacked to form a 128 Mb flash memory, or two 128-Mb flash memory chips may be stacked to form a 256 Mb flash memory. Because stacking semiconductor device packages may increase mounting density and the use of space, those in the industry have been actively working to develop improved stack structures as well as processes for fabricating semiconductor device packages.
FIGS. 1A, 1B, 2A, and 2B are sectional views illustrating a conventional procedure for stacking semiconductor devices. Referring to FIGS. 1A and 1B, semiconductor devices 20a and 20b may include via-electrodes 22a and 22b, respectively. The semiconductor devices 20a and 20b may have upper surfaces with bonding pads (not shown) and lower surfaces opposite to the upper surfaces. Via-electrodes 22a and 22b may be connected to the bonding pads (not shown) and may have upper parts (heads) protruding from the upper surfaces and lower parts (ends) protruding from the lower surfaces.
Semiconductor device 20a may be used as a base for a semiconductor device stack, and an adhesive film 30a may be formed on the upper surface of the semiconductor device 20a. The adhesive film 30a may include a patternable material that may be selectively etched (e.g., photolithography process) to expose at least a part of the head of via-electrode 22a. Semiconductor device 20b may be stacked on semiconductor device 20a by connecting the end of via-electrode 22b with the exposed head of the via-electrode 22a. 
Because the adhesive film 30a may be formed in a spin-on mode, the adhesive film 30a may have a higher density of solvent and photoactive compound (PAC) and a lower density of reactant for bonding. As a result, adhesion between the adhesive film 30a and the lower surface of the semiconductor device 20b may not be sufficient, thereby decreasing the reliability of the stacked structure.
Referring to FIGS. 2A and 2B, semiconductor devices 20a and 20b may include via-electrodes 22a and 22b, respectively. The semiconductor devices 20a and 20b may have upper surfaces with bonding pads (not shown) and lower surfaces opposite to the upper surfaces. Via-electrodes 22a and 22b may be connected to the bonding pads (not shown) and may have heads protruding from the upper surfaces and ends protruding from the lower surfaces. An adhesive film 60a may be formed to cover the upper surface of the semiconductor device 20a. The adhesive film 60a may include a material capable of being punctured, meaning that the material may be pierced without fragmenting into parts. To stack semiconductor device 20b on semiconductor device 20a, the end of via-electrode 22b may be used to puncture the adhesive film 60a so as to contact the head of via-electrode 22a, thus forming a stacked structure.
The adhesive film 60a may have improved adhesive properties because of its increased bonding density but may be difficult to pattern. Because it may be difficult to expose via electrode 22a by etching, via electrodes 22a and 22b may be electrically connected by puncturing the adhesive film 60a. However, despite its improved adhesive properties, unetched adhesive film 60a may result in an uneven mounting surface as illustrated in FIG. 2B, thus decreasing the contact areas for adhesion and resulting in decreased reliability of the stacked structure.